Fuse box of pyrex



April 10, 1934- A. G. STEINMAYER 1,954,186A

FUSE BOX OF' PYREX Patented Apr. 10, 1934 UNITED STATES PATENT OFFICE FUSE BOX OF PYREX Application June 5, 1931, Serial No. 542,217

Claims.

This invention relates to fuse boxes in generaly and more particularly to such boxes as are particularly adapted for outdoor use on high voltage systems. 5 Fuse boxes of the kind here contemplated generally comprise a housing of suitable insulating material provided with a hinged door or cover which is arranged to receive and hold the fuse. The box proper is provided with a pair of spaced terminal clips which are adapted to contact with corresponding clips or ferrules on the fuse when the cover, with a fuse mounted thereon, is swung to its closed position. The fuse box is generally provided with an opening for permitting the expulsion of gases or fusible metal when the fuse blows. When the cover of the fuse box is in its open position the line circuit is necessarily open. When repairs or alterations are to be made on a line it is essential that the circuit through the line be open and it is also essential, as a matter of safety, that the circuit through adjacent lines in the proximity of which a Workman may possibly approach, be also open. As a safety measure the practice has now arisen for a workman to require that the various fuse boxes of all the lines concerned be open before he commences working upon any line. As long as the workman is able to see that the cover of the fuse box is` in its open position he is assured that the correspondingA line circuit is dead and he can therefore work thereon with a reasonable degree of safety. It has now become the practice for power companies to instruct their linemen not to approach a line unless they see that the covers of the corresponding fuse boxes are open, and to insist that those covers be maintained open as long as he is working on the line. This procedure is necessary as a safety measure because if the fuse box cover is closed then the lineman has no way of knowing whether or not there is a fuse in position within the box and if there is such a fuse there is always the possibility that somebody at a distant point may apply voltage to the line.

The requirement that the fuse box covers be maintained in their open position during the making of repairs or alterations upon the lines introduces certain undesirable features. For instance, during rain or snow storms or during 50 other times when the air is charged with a large amount of moisture, the inner side of an open fuse box cover may become moist so that when the cover is ultimately'closed there is a film of moisture extending between the fuse terminals, 55 which introduces certain objections from the (Cl. 20o-133) point of view of the power company and also interferes with radio reception in the vicinity. This has heretofore been looked upon as the price to be paid for the safety and confidence given to the lineman as a result of his ability to 6g see the fuse box cover in its open position and to therefore know with certainty that the circuit to the line was open and could not be closed so long as the fuse box cover remained in its open position. It is one of the objects of the present invention to overcome the above mentioned objections incident to the leaving of the cover of the fuse box open, and yet to retain the safety afforded by being able to see that the line circuit is open. 'In order to attain this object I propose 70 to make the fuse box in such a manner that it is possible to see, by mere inspection, whether or not there is a fuse in the box, even though the cover be closed. Thus, in making repairs on a line, it is merely necessary to see to it that the fuse has been removed from the fuse box and then the cover can be closed. A lineman can, by merely glancing at the fuse box, tell if a fuse has been reinserted in place.. This object of the present invention is obtained by making the fuse 3;; box of a transparent material. I have found that Pyrex glass is admirably suited for this purpose.

The manufacture of Pyrex fuse boxes introduces certain problems not present in the manu- 35 facture of fuse boxes of porcelain. For instance, in the making of a porcelain fuse box, the box is first molded and after it has dried to a sumcient extent to permit its being handled it is removed from the mold and the side walls are drilled to provide openings through which the line conductors may extend to the terminals therein. Thereafter the box is baked or glazed. In the manufacture of a Pyrex box the drilling of holes through the Pyrex box is, to all intents and purposes, out of the question. It is therefore necessary to provide the holes by providing suitable cores in the mold. I have found that die casting is the most efficient way of making the Pyrex boxes but that it is impractical to attempt to mold the box with holes extending through the sides thereof for the reception of the line conductors. I have found that it is possible to make the box with the holes in the back thereof so that the holes extend i'n the direction of move- 105 ment of the mold, but it is practically impossible to make a box with the holes in the side of the box so that they extend at a substantial angle to the direction of movement of the mold. I have designed a form of box which lends itself admi- The holes for the lead-in conductors extend through the back wall of the box, which back wall is appreciably thicker than the side wall,

and they extend in the direction of movement of the mold.

In order to provide for the mounting of the box and in order to produce a more desirable electrostatic iield distribution at the point where the line conductors enter the box I propose to provide the rear wall ofthe box with an appreciably thickened portion which is adapted to receive the mounting means for the box and which is shaped to produce an elcient electrostatic eld distribution at that point.

The attainment of the above and further objects of the present invention will be apparent from the following specification taken in conjunction with the accompanying drawing forming a part thereof.

In the drawing:-

Figure 1 is a longitudinal sectional view through a fuse box `constructed in accordance with the teachings of my invention;

Figure 2 is a reduced front view of the box with the cover removed;

Figure 3 is a fragmentary sectional view of a portion of a similar box wherein the material at the rear side of the box is distributed in a somewhat diierent manner; and

Figure 4 shows a fragmentary portion of a still diierent arrangement.

Reference may now be had more particularly to the fuse box shown in Figures land 2. The 'box proper is made of Pyrex glass, or other transparent glass having high dielectric properties and able to withstand the hard usage to which such boxes are subject especially during the blowing of the fuse. The box comprises an integral body of glass having a back portion 1 and integrally formed side portions 2 and 3 merged together in a well rounded curve 4 which comprises the top of the box. The top and sides constitute a rim extending forwardly of the back portion. A forward projecting web 5 formed integrally with the back wall of the box divides the box into two more or less separate compartments one above the other. The web also strengthens the box and side walls.

Bushing structures 10 and 11 are formed integrally with the back wall and extend rearwardly thereof. These bushing structures include a central opening 12 which leads to an opening 13 of a somewhat reduced diameter; These openings are provided in order to permit the extension of a circuit into the fuse box between a pair of line Ihe outer side of the bushing 10v conductors. is provided with a number of circular grooves l5 and 16 which dene a number of receding circular flanges 17 and 18. This arrangement is provided in order to increase the moisture creepage area on the bushing structure and to obtain a better distribution of the electrostatic gradient between the live line conductor that is to be 1ocated within the opening 12 and the grounded part on the voutside of the bushing structure. The fuse box may be mounted in position in any desired manner, as.for instance by means of a pair of split clamps 20 and 21 which embrace the outsides of the bushing structures 10 and 1l. Any other mounting arrangement may be used but this arrangement is illustrated as a preferred form. v

A :flanged metallic tube which is threaded at its outer end extends through the opening 13 with its flange -26 bearing against the inside of the back wall of the fuse box. This tubular member is secured in place by means of a nut 27 which threads on its outer edge and through a suitable washer bears againstl the outer side of the rear wall 1 and provides a seal for preventing the entrance of moisture into the fuse box at this point. A terminal stud 30 which is provided with a socket 31 for receiving a line conductor, extends through the tubular member 25 and is secured against outward withdrawal by a cap nut 32 threaded thereon. The cap nut 32 also serves to secure a U-shaped spring contact clip 35 in place and to establish a firm electrical contact between the clip and the stud 30. The contact fingers of the spring clip 35 are of a form Well known in the art and are adapted to receive and -establish contact with the ferrule of a fuse or to establish contact with a clip on the cover of the box, to be hereinafter described, which clip holds a fuse. The terminal arrangement within the bushing structure l1 is of a construction identical with that in the bushing structure 10 above described.

A cover 40 which may also be made of Pyrex glass is hinged between the side walls 2 and 3 of the box by means of a hinge pin 41. The side walls and top portion 4 of the box are recessed to receive the cover so that when the cover is in its closed position it is surrounded by a rim 43 integral with the box proper, said rim preventing the entrance of moisture into the box. The cover 40 is provided with a pair of terminal clips 45 and 46. When the cover is in its open position a fuse 50 may be inserted between the terminal clips. The fuse may be of any well known construction and generally comprises a tube of insulation having a ferrule at one end thereof adapted to be received by the clip 45 and another ferrule spaced somewhat from the other end of the fuse Vand adapted to be received by the clip 46. A fuse wire is located within the tube 50 and extends downward through the open bottom of the tube and is bent upwardly and secured in electrical engagement with the ferrule adjacent the lower end of the fuse in any desired manner, as by means of a thumb screw 48. This type of fuse is well known in the art and does not, per se, constitute a part of the present invention. The contact clips 45 and 46 may be of any preferred construction so that they can receive and hold the fuse and in turn be received by and held in electrical engagement with the clip 35 and the corresponding clip at the lower side of the fuse box. The bottom of the fuse box is open as indicated at 55 so as to permit the expulsion of the gaseous and metallic products of a violent blowing of the fuse. A pair of spring members 56 and 57 are secured to the bottom sides of the walls 2 and 3 and cooperate with iiattened portions 58 and 59 at the edgesof the 'cover 40 for resiliently maintaining the cover in its open orin its closed position. As previously pointed out, the fuse box of the present invention is made of Pyrex glass and is preferably die cast. I have found that it is practically impossible to make a fuse box of this coring is formed in the direction of movement of the mold parts. However, if an attempt is made to form corresponding holes in the side walls then difliculties are encountered because of the necessity of a cross plunger for coring those holes. It is also to be noted that the openings or grooves 15 and 16 are also formed in the direction of movement of the dies. I have found that it is feasible to form indentations during molding of this material where the indentations do not necessarily extend in the direction of movement of the plunger of the die provided that those in- 'dentations do not extend entirely through the casting. Also due to the greatly thickened portion of the back Wall at the bushings 10 and 11 the coring of the holes 12 and 13 is greatly facilitated.

It is to be noted that my fuse box is transparent. A lineman may therefore close the cover 40 after he has removed the fuse 50 and even though the cover is closed he can tell at a glance whether or not the fuse has been replaced. Thus as long as the lineman is able to see that there is no fuse within the box he knows that he can work on the line with the assurance that the line is dead. It is not necessary for him to insist upon seeing the cover in its open position and therefore the cover need not be exposed to the accumulation of moisture while the lineman is working on the line.

In Figure 3 I have shown a terminal bushing 10 of a somewhat different construction from the terminal bushings of the box shown in Figure 1. This bushing differs from the previously described bushing in that here the cylindrical projecting portions 17 and 18' are located within the bushing structure rather than on the outside thereof. In other respects this form of bushing is indentical with that previously described.

In Figure 4 I have illustrated, in fragmentary form, a portion of a fuse box wherein the bushing structure is of a still different form. In this bushing arrangement the projecting rings 17 and 18 have been omitted and in place thereof there is a step formation 65, 66 and 67 forming cylindrical rings extending around the bushing structure and increasing the surface creepage area for moisture or the like. In other respects this bushing structure is identical with that pre- 'viously described.

In compliance with the requirementsof the patent statutes I have herein shown and described a few preferred forms of my invention. It is, however, to be understood that the invention is not limited to the precise arrangement herein shown but is capable of modification within the spirit and scope of the appended claims.

What I consider new and desire to secure by Letters Patent is:

1. A molded fuse box adapted to be mounted outdoors and exposed to weather, comprising an integral body of insulation having a comparatively thick back wall from which extends forward a comparatively narrow rim constituting side walls and a top integral with the back wall, the front of the box being open and adapted to be closed by a cover, the back wall having a pair of bushings of insulation extending therefrom and molded as an integral part of the back wall, each of the bushings having an opening extending longitudinally therethrough for extending a line circuit into the box, terminal studs securely held in place in the respective openings, spaced contact clips mounted on the terminal studs within the box, and a movable cover for the box, said cover including means for holding'a fuse and moving it into and out of circuit establishing position between the clips.

2. A molded fuse box adapted to be mounted outdoors and exposed to weather, comprising an integral transparent body of glass having a comparatively thick back wall from which extends forward a comparatively narrow rim constituting side walls and a top, the front of the box being open and adapted to be closed by a cover, the back wall having a pair of bushings integral therewith and extending therefrom, each of the bushings having an opening therethrough for extending a line circuit into the box, the openings in the bushings being formed in the molding of the box whereby the physical condition of the surface material at the openings is the same as that of the entire surface of the box, spaced contact clips mounted within the box adjacent the respective openings, circuit connections extending through the openings to the respective clips, a movable cover for the box, said cover including means for holding a fuse and moving it into and out of circuit establishing position between the clips, the fuse being moved to its open position upon opening of the cover, the box being transparent thus permitting inspection from a distance for visible discharges and fault and discharge producing conditions within the box when the cover is closed and a fuse is in its circuit establishing position between the terminals.

3. A molded fuse box adapted to be mounted outdoors and exposed to weather, comprising an integral transparent body of glass having a comparatively thick back wall from which extends forward a comparatively narrow rim constituting side walls and a top, the front of the box being open and adapted to be closed by a cover, the back wall having a pair of bushings integral therewith and extending therefrom, each of the bushings having an opening therethrough for extending a line circuit into the box, the openings in the bushings being formed in the molding of the box whereby the physical condition of the surface material at the openings is the same as that of the entire surface of the box, the creepage surfaces of the bushings being increased by circular convolutions comprising cylindrical projections extending axially of the openings and 125 formed as an integral part of the bushings, spaced contact clips mounted within the box adjacent the respective openings, circuit connections extending through the openings to the respective clips, a movable cover for the box, said 130 cover including means for holding a fuse and moving it into and out of circuit establishing position between the clips, the fuse being moved to its open position upon opening of the cover, the box being transparent thus permitting inspection from a distance for visible discharges and fault and discharge producing conditions within the box when the cover is closed and a fuse is in its circuit establishing position between the terminals.

4. A fuse box adapted to be mounted outdoors and exposed to weather, comprising an integral transparent body of cast glass having a comparatively thick back wall from which extends forward a comparatively narrow rim constituting 145 side walls and a top, the front of the box being open and adapted to be closed by a cover, said box having a pair of spaced openings therethrough for extending a line circuit into the box, said openings being formed in the casting of the 150 box whereby the physical condition of the surfacematerial at the openings is the same as that of the entire surface of the box, spaced contact clips mounted within the box adjacent the respective openings, circuit connections extending through the openings to the respective clips, a movable cover for the box, said cover including means for holding a fuse and moving it into and out of circuit establishing position between the clips, the fuse being moved to its open position upon opening of the cover, the box being transparent thus permitting inspection from a distance for Visible discharges and fault and discharge producing conditions within the box when cover is closed and a fuse is in its circuit establishing position between the terminals.

5. A molded use box'adapted to be mounted outdoors and exposed to weather, comprising an integral body of insulation having a comparatively thick back wall from which extends forward a comparatively narrow rim constituting 'side walls and a top integral with the back wall,

the front of the box being open and adapted to be closed by a cover, the back wall having a pair of bushings of insulation extending therefrom and molded as an integral part of the back Wall, each of the bushings having an opening extending longitudinally therethrough for extending a line circuit into the box, each of said openings being of reduced diameter adjacent its inner end to form a shoulder, a stud extending through the opening and clamped againstthe inner and outer faces of the shoulder, means securing a contact clip to one end of the stud, said meansholding the stud against retraction, and means at the other end of the stud for establishing a connection with a conductor.

ALWIN G. STEIN'MAYER. 

